android AudioRecord中的BufferSize减小

Question

I am trying to live streaming in android to a server. My program is working fine.

The method which starts streaming is:

private void startStreaming() {

    Thread startRecord = new Thread(
            new Runnable() {
                @Override
                public void run() {
                    try {
                        socket = new DatagramSocket();
                    } catch (SocketException e) {
                        e.printStackTrace();
                    }

                    buffer = new byte[minBufSize];

                    DatagramPacket packet;

                    try {
                         destination = InetAddress.getByName("10.31.0.12");
                    } catch (UnknownHostException e) {
                        e.printStackTrace();
                    }

                    record = new AudioRecord(MediaRecorder.AudioSource.MIC,sampleRate,channelConfig,audioFormat,minBufSize * 10);

                    record.startRecording();

                    while ( status )
                    {
                        minBufSize = record.read(buffer,0,buffer.length);
                        packet = new DatagramPacket(buffer,buffer.length,destination,port);
                        Log.d(LOG,"Writing in status " + destination );
                        try {
                            Log.d(LOG, "Trying to send. " + minBufSize);
                            socket.send(packet);
                            Log.d(LOG, "Sent successfully.");
                        } catch (IOException e) {

                            Log.d(LOG,"Socket is not sending properly.");
                            e.printStackTrace();
                        }
                    }

                }
            }
    );
    startRecord.start();
}

The method which stops recording :

public void stopRecording(View view) {
    start.setVisibility(View.VISIBLE);
    stop.setVisibility(View.GONE);
    status = false;
    Log.d(LOG,"I am about to release the record.");
    record.release();
    Log.d(LOG, "I have released.");
}

I am getting minBufSize using

 minBufSize = record.read(buffer,0,buffer.length);

If I keep stopping and playing recording, the minBufSize keeps on decreasing. Values changes from 1280 to 512 to 256 to -3 and finally I am getting :

java.lang.NegativeArraySizeException: -3 at
com.example.khan.safevoicerecorder.MainActivity$1.run(MainActivity.java:81)

Why is this happening? Please help me to solve this.

Answer 1

You create buffer using the current minBufSize . Then, your loop reads for a while: minBufSize = record.read(buffer,0,buffer.length) . Since the read will be at most buffer.length bytes, you may now have decreased minBufSize .

The next time you start a recording, your buffer will be created with the new, smaller minBufSize . Again, the read will be at most buffer.length bytes (which is now smaller than the last time).

Rinse and repeat -- then eventually, you'll get a very small buffer. I'm guessing that gives you the -3 error value. And finally, when minBufSize is -3 , your buffer allocation will fail; an array can't have a negative size.